Drilling fluid composition and process



United States Patent 3,244,623 DRILLING FLUID COMPOSITION AND PROCESS Ellis Gray King and Carl Adolphson, Bellingham, Wash,

assignors to Georgia-Pacific Corporation, a corporation of Georgia No Drawing. Application Apr. 1, 1960, Ser. No. 19,167, which is a division of application Ser. No. 815,294, May 25, 1959. Divided and this application Nov. 8, 1962, Ser. No. 236,426

28 Claims. (Cl. 252-85) This application is a divisional application based on our copending application Serial No. 19,167, filed April 1, 1960, now US. Patent No. 3,087,923, which in turn is a divisional application based on our application Serial No. 815,294, filed May 25, 1959, now US. Patent No. 2,935,473, which in turn was a continuation-in-part of our copending application Serial No. 433,794, filed June 1, 1954, now abandoned, entitled, Process of Improving the Effectiveness of the Components of Spent Sulfite Liquor and the Products Thereof; our copending application Serial No. 539,542, filed October 10, 1955, entitled, Process of Improving the Effectiveness of the Components of Spent Sulfite Liquor and the Products Thereof, now U.S. Patent No. 2,935,504; our copending application Serial No. 769,185, filed October 23, 1958, entitled, Process for Providing an Improved Drilling Fluid and the Product Thereof, now US Patent No. 3,171,810; our copending application Serial No. 789,775, filed January 29, 1959, now abandoned, entitled, Process for Providing an Improved Drilling Mud of Clay and a Metal Lignosulfonate and the Product Thereof; and our copending application Serial No. 806,974, filed April 16, 1959, now abandoned, entitled, Improved Gypsum Base Drilling Fluid and the Products Thereof. The methods of treating sulfonated lignin-containing material through oxidation and salt formation in improving the dispersive properties of said sulfonated lignin-containing material and the combination of said additive products with clay and water in forming drilling muds are completely disclosed in said copending applications. Furthermore the unexpected resistance of such muds to the contaminants encountered in oil Well drilling was also set forth.

Our invention and discovery relates to improvements in drilling fluids resulting from a novel combination of clays and specially treated sulfonated lignin-containing material.

More particularly our invention relates to an improved drilling fluid or mud composition or combination, and to a process for use thereof, This mud combination may be formulated to function as water base drilling muds, for example and not limitation as fresh Water mud, as lime base mud, as gypsum mud, as calcium chloride mud, as salt contaminated or sea water muds, and in emulsion mud systems. Furthemore, the mud combination is usable over the entire pH range of drilling mud fluids used in the field. A particularly novel form of our mud system is the combination with gypsum which is especially useful in drilling oil wells when anhydrite is encountered. I-Ieretofore, a well recognized fact is that sulfonated lignin-containing additives such as those derived from spent sulfite liquor are effective as thinners in lime base muds but such are not useful as thinners in fresh water muds.

Moreover, our improved mud combination is characterized by stability to high temperature and by effectiveness in resisting the deteriorating effects of contaminants encountered in drilling. Such effectiveness is particularly advantageous in drilling deep wells where high temperature and pressure exists.

Our invention and discovery herein relates primarily and fundamentally to the providing of a novel combination of drilling mud clay and sulfonated lignin-containing material whereby there results drilling muds of newly found properties. It would be difficult to find a more. sensitive test of the increased effectiveness of the components of our invention than those required to meet the properties of said drilling muds.

The improved effectiveness of the components or" the sulfonated lignin-containing material provided by our invention and discovery results in the production of an improved drilling mud, which mud is characterized by having greatly improved properties.

The outstanding properties of suitable magnitude which characterize a useable and practical drilling mud comprise the following: (1) initial gel strength; (2) viscosity; (3) 10-minute gel strength; and (4) water loss, which relates to the sealing off of the wall of the drilling hole by building up a filter cake of mud on the wall, thus preventing loss of water from the mud. Thus, it is manifest that the drilling mud, with its exacting requirements of various properties for the mud, is a most important, involved, and complex feature of oil and gas well drilling.

Universally, a drilling mud (having about the consistency of lubricating oil) is used in a circulating system with rotary well drilling mechanism, and is forced by pumping down the hollow drill stem through the bit which it lubricates and cools, then back to the surface to a settling pit. Thus it washes out the cuttings'which have been made from the hole, and the cuttings are carried out side the drill stem to the surface where the coarse particles are caused to be removed and the mud again used in a continuous circulating process. To prevent the loss of the mud in porous strata, the mud must be of a character to seal off such strata and the mud, by its hydrostatic pressure, must prevent the escape of gas, that is prevent the Well from blowing out. To provide the proper hydrostatic pressure, the specific gravity of the mud may be increased by adding heavier material than clay, such as barytes. On the other hand the drilling fluid must have the proper viscosity, that is, be thick enough to carry out the cuttings, but thin enough to be pumped and to allow the coarse particles to'settle out in the surface mud pits so that the mud may be re-used.

Our invention and discovery is characterized by making it possible to greatly improve the effectiveness of the components of said sulfonated lignin-containing material with very simple and inexpensive equipment. The simplicity of the treatment of our invention and discovery isone of its outstanding features.

One important property of drilling mud is that in case of temporary stoppage of work, the mud should gel sufficiently to prevent settling of the suspended cuttings, which settled cuttings would seize the drill stem and prevent re-starting or its withdrawal from the wall. From this it is manifest that the viscosity of the fluid is highly important. Likewise, the property to gel or to set like gelatin is important when the agitation incident to drilling ceases. Thus, the mud will hold in suspension the cuttings and at the same time become fluid when agitation is resumed. This is called the thixotropic property of the fluid, or its gel strength. Most clays have this property but not all. Such property may be increased by adding the clay called bentonite and similar substances. As the drilling proceeds through different strata, the viscosity and gel strength may be alfected by the character of the strata, by the loss of absorption of water in the porous strata or in the inflow of water and other fluids, by temperature changes, or by chemically active substances which may enter the drilling fluid as the drilling proceeds. Accordingly viscosity, gel and water loss are very carefully watched and corrected from time to time during the drilling. There are'instruments prtfi ided for testing such properties at the mouth of the we In the early history of well drilling, water was added to thin the mud, but this had the objectionable result of reducing the specific gravity of the drilling fluid and thereby decreased its hydrostatic pressure property, and also described its ability to suspend the cuttings and the barytes which had been added to give weight. Also, to overcome the effect of addition of chemicals from the strata through which the well proceeded, i.e., the effect from so-called contaminants, other chemicals were added to offset the deleterious effects.

In fact, the literature relating to drilling rnuds is so extensive and comprehensive and has extended over such a long period of time that it is very apparent that impo.- tant difficulties, mechanical, chemical and economical, are involved in the controlling, conditioning, and obtaining of the proper type of drilling mud. It is one of the fundamental objects and purposes of this invention and discovery to provide a drilling fluid containing an inexpensive and highly effective mud additive to overcome the problems that have existed for so long in this field. Let it always be kept in mind that the value of the drilling mud depends on how much it will contribute to speed, efficiency, and safety in oil and gas well drilling. Our invention and discovery provides a combination of clay and treated sulfonated lignin-containing material, which combination is characterized by its economy as well as its very special effectiveness, not only for one of the two primary recognized types of drilling muds, i.e., lime base and fresh water rnuds, but for the special effectiveness of both of said types of mud.

An important and fundamental object of our invention is to provide a gypsum base mud characterized by a low gel rate rather than the usual objectionable high gel rate which is usually accompanied by high fiat gels. Such rnuds accomplish the maintaining of suitable gels so that cuttings fall out in the mud pit without the necessity of watering back to thin the mud. In this way, the need for costly water loss reducing agents such as carboxymethylcellulose is substantially lessened, if not eliminated, and the amount of expensive weighting agents required for deep wells is decreased.

RELATIVE CONTAMINANTS In the drilling of deep wells such as oil and gas by the employment of a mud laden drilling fluid as in the rotary system of drilling, strata of a contaminating character may be encountered in large masses which often supply calcium sulfate to the drilling mud-this is very disadvantageous and alters or destroys required properties of the mud. Such calcium sulfate may be, among other forms, in the form of gypsum (calcium sulfate with water of crystallization) and anhydrite (calcium sulfate without water of crystallization). The literature states (Rogers, Composition and Properties of Oil Well Drilling Fluids, page 377):

The first small additions of calcium sulfate increase the viscosity and gel strength of the mud fluid greatly but do not increase the fluid loss appreciably. This peak portion of the viscosity curve is reached at an addition of 33.3 p.p.m. calcium per gram of bentonite. As the concentration of calcium sulfate increases, the viscosity decreases and the fluid loss increases sharply.

As the concentration of the calcium sulfate increases, the viscosity decreases and the fluid loss increases sharply-obviously this feature evidences unpredictable character of contaminants upon the components of the drilling rnuds as respects the important properties which must characterize the mud. The different properties of the mud are affected differently. Rogers further states (said text, page 378):

unfortunately, the addition of the soluble sodium sulfate results in a large increase in viscosity and gel strength. This effect is of such a magnitude that the 4 method cannot be used in the field to overcome the adverse effects of the anhydrite. It can, however, be demonstrated in the laboratory.

The discovery and invention herein disclosed shows how this objectionable feature of sodium sulfate has been overcome, and to this extent the invention and discovery of applicants is contrary to the recognized literature in this field.

Other contaminating strata are salt beds and the cement employed in the construction of the well. Also let it be noted that the contaminants may be a combination of the contaminants disclosed herein.

It is the primary and fundamental purpose of our invention and discovery to provide a drilling mud system or combination of clay and sulfonated lignin containing material which will operate in controlling the colloidal and physical properties and for maintaining the required properties of a water-clay drilling mud which may be subject to contaminants, so that the mud combination will function in a more effective and more economical manner than heretofore. Thus, an important part of our invention is the rendering more effective the properties of the sulfonated lignin containing materials and herein resides protection against contamination.

This part of our invention relating to the sulfonated lignin containing materials is commonly referred to as the drilling mud additive. Our purpose is to provide such an additive of a character which will function as a control product for the colloidal and physical properties and for maintaining the required properties of the water clay drilling mud which may become subject to contaminants in the drilling operation and to provide such an additive when combined with the mud that will function in a more efficient and more economical manner than has been accomplished heretofore.

The part of our invention and discovery which relates to a further improvement in lessening water loss of gypsum contaminated muds involves the addition of sodium sulfate or equivalents as hereinafter listed to the combination of clayey material and the additive lignosulfonate product of our invention and discovery, in the proportion of 1% to of said sodium sulfate or equivalents by weight of the additive lignosulfonate product, said addition being made in proportions determined by a pilot test of a drilling mud which is contaminated with calcium sulfate. The additive product of our invention in and of itself may not produce the extremely low Water losses desired in some rnuds. The addition of the sodium sulfate and equivalents as hereinafter listed will further reduce the water loss to the desired level and at the same time said additive product prevents the large rise in viscosity and gel factors which occur when sodium sulfate alone is added to an aqueous suspension of clayey material. Thus in the presence of the additive lignosulfonate product, the ordinary adverse action of the sodium sulfate is depressed.

Sometimes the formations are of thick dolomitic lime or other rock sections which do not contribute good mud making materials. In such cases it is necessary to control or maintain the mud by addition daily of bentonite to develop the desired low fluid loss, and the pH of the mud is maintained on the alkaline side to promote hydration and dispersion of the drilled shales. The alkaline pH promotes higher viscosities in the bentonite clays, and, therefore, thinners are added and those with alkaline properties such as the sodium tannate type are preferred. These thinners, because of the presence of alkaline sodium salt, aid in the formation of sodium clays from the dispersed shales and also increase the degree of dispersion of the clays and shales and hence reduce the fluid loss to strata surrounding the hole. In general, the pH or alkalinity of such rnuds is maintained at about 9.0 or 10.0. At times the pH of the mud rises or is carried to the range of 10.5 to 11.5 in which the clays and bentonite present manifest appreciably higher 'when fresh water is not readily available.

viscosity. The treatment of these muds is with sodium hydroxide and quebracho (sodium tannate), and they are referred to as red muds. In all of these cases, the principal contaminants are salt, cement, gypsum or anhydrite, sand, and other inert mineral matter.

When the mud viscosity becomes too high, it may be more economical to convert to the so-called lime base mud rather than to dilute with water involving the necessary addition of weighting material. At other times, the contamination becomes so bad that the chemicals are not effective and it is found necessary to convert to the lime base mud. This conversion involves the addition of an excess of lime and caustic together with a thinner such as quebracho or, preferably, lignosulfonates. This type of high pH mud with an excess of lime is hereinafter referred to as a lime base mud as contrasted to all of the other water clay muds previously discussed, which for convenience will be hereinafter termed fresh water muds.

OBJECTS In general, quebracho, as a thinner, has been used in all types of muds, both fresh water and lime base, but quebracho is an expensive commodity. To date, the lignosulfonates have been useful only in lime base muds where they are well known to be relatively inexpensive, but until now, i.e., until the present invention, it has not been possible to use the lignosulfonates in the lower pH (less than 12, Le, fresh water) muds not containing an excess of lime, inasmuch as they have no appreciable thinning action on such muds. One of the primary objects of this invention is to provide a drilling fluid composition containing an additive comprising a soluble sulfonated lignin-containing material which is highly effective, not only as lime base muds, but also as fresh water type muds.

A primary and fundamental object is to provide a drilling fluid containing a dispersing agent derived from spent wood pulping liquor solids in the simplest and most economical manner with relatively inexpensive equipment, and in a continuous manner to produce from these said liquor solids a soluble additive for drilling mud systems or combinations which is elfective in reducing the viscosity and gels of both fresh water muds and the so-called lime base muds, even in the presence of substantial quantities of natural contaminants such as anhydrite, sodium chloride and sodium sulphate.

Another objective is to provide by a sequence of steps a drilling fluid containing an additive derived from spent wood pulping liquors which are preferably initially purified and fractionated and then modified to obtain a soluble additive for making the mud combination of our invention which is characterized by the fact that molecules of each fraction are of a particular and different molecular average size and especially useful for dispersing agents in general and additives for drilling muds in particular.

Another primary object of our invention is to provide a drilling fluid containing an additive produced by preparing and fractionating chlorinated lignosulfonates to provide said chlorolignosulfonates in fractions of specific molecular weight to adapt the same to a particular purpose. It is particularly the object of this invention to provide drilling fluid compositions containing soluble spent sulfite liquor additives that are not only especially lower in cost, but are highly effective and useful in essentially all types of water clay and oil-in-water emulsion drilling muds.

Still another object of this invention is to provide a drilling mud which is prepared with saline or sea water Mud prepared with sea water has special utility in off-shore drilling 'Where fresh water must be transported to the drilling site and fresh water muds must be protected from sea water contamination. We have found that the additive of our invention is surprisingly effective as a thinner 6 not only for gypsum base muds, but also for saline muds made up originally with sea water as the aqueous component together with commercial drilling mud clays.

A further object of the present invention is to provide a drilling fluid containing an additive comprising sulfonated lignin-containing material which has been treated at high temperatures to improve its properties.

DEFINING STARTING MATERIALS Spent lignin liquors from the pulping of wood provide an inexpensive source of the raw material for our process and product, the said liquors being available in large quantity as waste products of the pulping processes. One of our aims is to conserve this waste material.

The preferred raw material is derived from the pulping of Wood by the calcium bisulfite process for the manufacture of pulp. In this operation a substantial portion (20% to 70%, usually about 55%) of the wood is converted to water soluble products which at the end of the cooking process are separated from the pulp in water solution. This solution, because of the washings, is very dilute, ranging approximately from 5% to 20% solids. This solution can be used as such in our process or it can be concentrated in any one of several well known ways to a more concentrated solution which is more readily and economically handled, particularly because of the smaller volume of liquid involved. The concentrated solution can range from 30% to 70%, but handles better in the range of 40% to 50% totalsolids in solution. This concentration solution contains lignosulfonates as salts (for example calcium, magnesium, sodium, or ammonium salts, depending on which of these are employed in the digesting process), carbohydrates, and other complex organic compounds derived from wood, as Well as inorganic compounds either present in the wood or derived from the reaction. Furthermore, digesting of wood by iron or aluminum bisulfite will give a spent 'sulfite liquor componentwhich may be our raw material and which will obviate the necessity of a base exchange reaction to form the iron or aluminum salts. The concentrated solution may be used in our invention and it is very desirable to do so. However, the spent sulfite liquor can be further refined before or after processing according to our invention. For example, the spent sulfite liquor can be essentially freed of carbohydrate material by any one of a number of procedures, preferably by fermentation. Also, said carbohydrates may be removed by dialysis, by separation with organic solvents or organic bases, or by precipitation as basic lignosulfonates, for example, with lime or by salting out with salts such as calcium chloride or sodium chloride. In addition, the lignosulfonates, as well as being freed as far as possible of extraneous materials. may be fractionated as to molecular weight components.

Any of these above described products are basically derived from spent sulfite liquor solids, and are sulfonated lignin-containing materials and the degree of refining to which they are subjected either before or after the steps of our invention will depend on the quality of product desired and the economics involved. That is, refining to some extent will improve the properties of the final processed product, but the degree of improvement will not always be economically justifiable. In fact, it is an essential and outstanding feature of our invention and discovery that we can use concentrated spent sulfite liquor as such, and through a series of simple steps involving equipment which is relatively inexpensive, can produce products which are equivalent in properties, for instance, for use as drilling mud additives and dispersants, to the purified lignosulfonates.

In general, any type of wood or lignocellulosic material, the same including straw, cornstalks, bagasse and the like, which can be resolved to pulp with the separation of the lignin-containing material, may be used as a source for providing lignosulfonate in following our invention. Furthermore, changes in the final properties of the product are influenced by the conditions of the pulp process, but in general good results are obtained using the commercial spent sulfite liquor from either paper grade quality pulp or dissolving grade quality pulp.

In addition to the spent sulfite liquor derived from the acid bisulfite pulping of wood, liquors containing soluble lignin are also available from the neutral and alkaline pulping of wood or other lignocellulosic material. Such lignin-containing materials may be converted to sulfonated lignin-containing materials usable as raw materials for the process of our invention, for instance by treatment with sulfites at elevated temperatures, chlorination and heating with sodium sulfite or by other methods known to those skilled in the art, subject only to getting a soluble sulfonated lignin or one which tends to dissolve in water and which on forming the metallic salt and being oxidized is soluble. For example and not by way of limitation, sulfonated Kraft lignin has been found to perform well in making the oxidized metallic salts of sulfonated lignin according to our disclosure. This is also true of sulfonated soda lignin.

In deriving sulfonated lignin containing material from wood pulping liquors varying degrees of sulfonated lignincontaining material result, depending on the well known range of conditions involved in the different methods of sulfonation. For practicing our invention the resulting sulfonated raw material should be soluble in water or in highly alkaline aqueous media and should have dispersing properties. These characteristics are in part associated with the degree of sulfonation, or the proportion of sulfonic acid groups which have entered the lignin molecule during the sulfonation process. The chemical formula for sulfonic acid groups is SO H, in which the sulfur atom is combined directly with a carbon atom in the lignin or other organic material in the lignin-containing material sulfonated.

This type of sulfur is to be distinguished from inorganic sulfates or sulfites, sulfur dioxide free or loosely combined with the lignin and sulfur which might be bound with the lignin as a sulfate. The sulfonate sulfur or sulfur combined directly with carbon is a stably bound sulfur which is not removed from the lignin without drastic treatment such as with sodium hydroxide at high temperature and pressure. In speaking of the sulfur content of the sulfonated lignin-containing material, we refer to the total sulfur as the sulfur of all types which are determined by standard analytical procedures and to the sulfonate sulfur which is the sulfur stably bound with the lignin. The degree of sulfonation required to promote solubility and dispersive properties will vary somewhat with the source of the lignin being sulfonated, i.e., the conditions of pulping. However, sulfonated lignin, having sulfonate sulfur contents as low as those in the range 0.93.8% have been used successfully in making the dispersive additives of our invention. Products containing sulfonate sulfur in excess of these amounts do, of course, have the requisite solubility for use in accordance with the present invention.

By way of summary, the raw material for our process is a sulfonated lignin-containing material as it may be received from the blow pit of the bisulfite process or modification of said bisulfite process employing somewhat less acidity, for example and not limitation, about pH 4.5 instead of 1.5 or less, or other sulfonated lignin-containing materials such as those derived from neutral or alkaline pulping processes. Any of these may be in any one of a number of states or degrees of refinement, purification and concentration. We prefer, however, to use concentrated and fermented spent sulfite liquor from the pulping of wood with calcium bisulfite cooking acid because such material is already sulfonated, and is easily converted to other metal salts as disclosed hereinafter and is available in large quantities. By fermented is meant spent liquor from which carbohydrates have been removed by fermentation. In any event our starting material comprises a sulfonated lignin-containing material.

Our starting material may be refined and fractionated, but whether it is fractionated before or after treatment according to our invention depends on economical considerations and the special product desired.

Briefly stated, our novel compositions include additives produced by a process which in part involves converting sulfonated lignin-containing material to a salt of iron, chromium, copper, and aluminum, or combinations of said salts; or converting the refined sulfonated lignincontaining material to said salts; or converting the fractionated sulfonated lignin-containing material to said salts; or converting to said metal salts sulfonated lignin material subjected to other pretreatments, effecting improvement in properties for use in drilling mud, for example but not by limitation, by alkaline heat pretreatment as set forth in our copending application Ser. No. 694,737, filed November 6, 1957, acid heat pretreatment, and pretreatment by steam stripping, gas or air blowing during heating of solutions of said sulfonated lignin-containing materials derived from spent wood pulping liquors. Said acid treatment may be carried out at less than about pH 4 at temperatures from 50 C. to 180 C. for times causing polymerization or thickening of the solution short of gelation, as set forth in US. patent application 723,036, filed December 18, 1957, as a continuation-in-part of our US. patent application Serial No. 433,794, filed June 1, 1954, and Serial No. 539,542, filed October 10, 1955. At higher pH, heating may be conducted at temperatures of C. to 210 C. to bring about similar polymerization of thickening of the solution short of gelation.

Another feature of the invention comprises the use of drilling fluid additives prepared by a process which involves subjecting the sulfonated lignin-containing material containing said metallic salts to oxidation which brings about changes in the constitution of the solids of the sulfonated lignin-containing material resulting in additives of greatly enhanced properties comparable and superior to those of natural quebracho in the making of drilling muds.

Also, liquor containing the said metallic salts of dissolved fractionated components may be subjected to oxidation which brings about changes in the constitution of the fractionated solids of the sulfonated lignin-containing materials resulting also in additives of greatly enhanced properties comparable and superior to those of natural quebracho in making drilling muds. Our products are also superior in dispersing the ingredients of clay slips, cement, plaster, etc.

The fact that the original spent sulfite liquor may be oxidized directly and converted to the said metallic salts, forming an additive which is effective in both fresh water and lime base muds, manifests how very economical may be the products of our invention for such special uses.

Another feature of the present invention comprises the use of drilling fluid additives prepared by a process which involves the oxidation of sulfonated lignin-containing material, regardless of Whether the salt of iron, chromium, copper and/or aluminum is formed. We have found that such oxidized materials make substantial improvements in the effectiveness of thinning of lime base drilling muds. However, said products also provide substantial improvement, although to a lesser degree than is provided by combining oxidation with salt formation, in the case of fresh water drilling muds.

In making the salts of iron, aluminum, copper, or chromium of sulfite liquor which, for the production of an oxidized salt, can be done either before or after oxidation, we prefer to use the sulfates of these elements for this purpose because with calcium base sulfite liquor, calcium sulfate precipitates so that it may be removed and thereby bring about purification of the product. Higher temperature promotes the growth of larger crystals of calcium sulfate which are easier to separate from the liquor, hence it is desirable to hold the liquor after addition of the sulfate at 9095 C. for a period of time. The formation of large crystals is also fostered by bringing about the interaction of the salt with the spent sulfite liquor solids in such a manner that the precipitation of the calcium sulfate occurs more slowly. This objective can be accomplished by using more dilute solutions and/ or using lower temperatures during the base exchange reaction. Hence, a preferred method of forming the iron, chromium, copper, and aluminum salts is to carry the reaction at 3050 C. and then to heat the solution with agitation to 9095 C. and hold this temperature for one hour or longer. The reaction mixture is usually acidic during this stage so that this latter treatment is also an acid treatment and has beneficial action on the properties of the spent sulfite liquor product.

Aluminum sulfate may be added preferably in proportion equivalent to the base (i.e., calcium, sodium, magnesium and ammonium) already present in the spent sulfite liquor or it can be used in smaller or greater proportions. Furthermore, aluminum sulfate may be added in anhydrous form or as any of the hydrates of comrnerce, such as paper makers alum (17% A1 or as Al (SO -l8H O. In making the lignosulfonate salts, we have used aluminum sulfate salts in the proportion of 1% to 50% by weight of the spent sulfite liquor solids. With the other salts, i.e., iron, chromium and copper, the range of permissible addition is about the same, i.e., 1% to 50%. For example, copper requires the addition of about 30% of CuSO -5H O for complete base exchange as compared with about 26% of A1 (SO.;) l8H O which takes into consideration the usual chemical equivalence. However, good results have been obtained in using from 15% to 30% of aluminum sulfate (Al (SO -18H O). The same observation applies to the use of iron, chromium, and copper salts.

In addition to adding sufficient of the cations to be equivalent to approximately the base present in the sulfonated lignin-containing material, it is our unusual (and unexpected) discovery that an excess of the cation over the chemical equivalent for base exchange improves the effectiveness of the product of our invention and discovery, particularly in respect to the conditioning of fresh water mud in connection with obtaining the lowest possible values for yield value and min. gel and water loss. Thus in the preparation of fresh water muds, we prefer to add an excess of a sulfate salt having a cation selected from the group: iron, aluminum, copper and chromium, or mixtures thereof. Since these salts occur as hydrates with varying amounts of water, the permissible addition of these salts to the mud is more definitely expressed as an amount of the sulfate salt equivalent to the anhydrous form of that salt. Thus in terms of the anhydrous forms, the permissible addition is about 1% to 80% by weight of the sulfonated lignin, in excess of the amount of sulfate salt necessary for the base exchange. Thus, for example, with the ferric sulfate the optimum results are obtained with a total addition of the sulfate salt of about 40% to 50% by weight of the sulfonated lignin, which on the anhydrous basis, would be about 35% to 42% by weight. Accordingly, the excess over the amount for chemical equivalence on the anhydrous basis is about 20% to 27%. Ferrous sulfate and the sulfates of aluminum, chromium and copper perform in the same manner and the excess addition over the chemical equivalent on an anhydrous basis is also about 1% to 80%. Mixtures of these sulfate salts can be used for this purpose. Copper has the advantage of imparting antiseptic properties to the additive, to preserve the mud which may be subject to micro-biological attack, par- .ticularly so when starch is present.

In regard to the permissible addition of excess sulfate salt the disclosure above of 1 to 80% by weight of the anhydrous sulfate salt pertains to the salt and not to the oxidized salt. For the latter the permissible addition is somewhat less than 70%. Accordingly, from the standpoint of commercial practicability, as applied to both the salt and the oxidized salt, an excess of 1 to 50% of the anhydrous sulfate salt on the basis of the sulfonated lignin is preferred.

In forming the said salts of the sulfonated lignin-containing material, it is preferable to have the latter in the calcium condition, that is, as a calcium salt so that when the sulfate salts of iron, aluminum, copper and chromium are added, the base exchange reaction occurs and calcium sulfate forms which can be removed, thus yielding an essentially pure form of the desired salt.

The disclosure above relating to the permissible addition of 1 to pertains particularly to sulfate salts, or any salt of said metals the anions of which form insoluble salts with calcium, for example, oxalates. However, any soluble salt of these metals could be added to a solution of the sulfonated lignin-containing material without the formation and/or removal of a precipitate. The anion in said soluble salt may be any of the common anions such as, chloride, nitrate, formate, etc., although higher concentrations of chloride ions and to a lesser extent nitrate ions become deleterious above the concentration equivalent to the base exchange capacity of the sulfonated lignin. Continuing then, when such a solution is brought to dryness, because of the ionic equilibrium in the solution, a mixture of salts is obtained. Thus, an amount of the desired lignosulfonate salt, for example, iron, Would be present in the product, together with the base (sodium, magnesium, ammonium, etc.) which was originally in the sulfonated lignin-containing material. This product would not be as efficient as the product in which the original base in the sulfonated lignin-containing material was removed prior to or on addition of the iron salts. However, in cases where the sulfonated lignin-containing material has the base sodium, magnesium or ammonium present instead of calcium, it may be satisfactory to make the partial salt in the aforesaid manner. This could be the case, for example, with sulfonated lignin from the Kraft and soda processes which usually contains sodium as the base by reason of the steps of its manufacture.

When an excess of a soluble inorganic salt (including salts such as formates and oxalates under the designation inorganic) of iron, chromium, aluminum, or copper over and above the stoichiometric equivalent of the sulfonated lignin is added in preparing the product of our invention, and the added anions are not subsequently removed, a product is obtained which is less efficient as a thinner but nevertheless is effective. The lower efficiency results from (1) dilution of the thinner by the soluble inorganic salts, and (2) a thickening of the mud resulting from the small amount of soluble inorganic salt added to the mud as a component of the thinner product. Thus, the thinner product with the excess appears to be inefficient when used in small amounts but when large amounts of said thinner product is added to the mud, the surprising resistance of the sulfonated lignin metal complex to the salt contamination overcomes the effect of the small amount of inorganic salt.

The salt contamination effect may be illustrated by considering the combination of one part of ferric chloride with 2 parts by weight of thinner additive of our invention. This combination would amount to 50% of excess of ferric chloride. Adding 9 pounds per barrel of this combination to the drilling mud gives a chloride concentration in the mud approximately equivalent to 3 pounds per barrel of sodium chloride or about 1% of said chloride and a thinner additive concentration of about 6 pounds per barrel. A mud contaminated with 1% salt (sodium chloride) is readily thinned by 6 pounds per barrel of the thinner additive.

The amount of metal for complete base exchange will depend on the concentration of acidic components in the sulfonated lignin-containing material and in particular the concentration of the sulfonated lignin. By way of example and not limitation fermented spent sulfite liquor solids having a sulfone sulfur content of about 6% will require about of iron for base exchange. The addition of 50% excess anhydrous ferric sulfate over that required for base exchange is equivalent to about 14% of iron.

When magnesium, ammonium, or sodium 'bisulfite cooking liquor instead of calcium has been used in manufacturing the pulp, it is then desirable, but not absolutely necessary, to eliminate or partially eliminate the magnesium, ammonium, or sodium ions prior to making the iron, chromium, cooper, or aluminum salt. This situation can be brought about by converting to the calcium salt before proceeding with the process of our invention, or it can be accomplished by any number of procedures well known to those skilled in the artfor example, by ion exchange, dialysis with addition of acids, and base exchange procedures in general. For example, cations (i.e., magnesium, ammonium, or sodium) may be removed by passing the liquor through a cation exchange column in the hydrogen state, and then treated with an oxide or hydroxide of iron, chromium, copper or aluminum. We prefer to have the lignosulfonate in the form of the calcium salts before making the iron, chromium, copper, and aluminum salts because the salts are obtained with less contamination in this manner by reason of the calcium sulfate being precipitated so it can be removed-but note well, such purified products can be obtained by any procedure known to the art for making the conversion to the desired salt as well as those named immediately above.

An example of partial salt formation comes as a result of the oxidation treatment with sodium or potassium dichromate as a result of the fact that chromium salts are a product of the reactions involved. Any soluble chromium salts thus formed will provide chromium ions which will be in equilibrium with the calcium ions associated with the sulfonate group of the lignosulfonate. Thus, a partial chromium salt of the lignosulfonate in essence will be formed which would tend to impart the properties attained if the calcium were removed and the lignosulfonate salt were wholly chromium salts. If, furthermore, an excess over the amount of sodium dichromate necessary for the base exchange, i.e., about 12% of sodium dichromate, is added, additional chromium ions resulting from the reduction of the dichromate are present which tend to drive the reaction in the direction of the formation of the chromium salt of the lignosulfonate so that this excess would have somewhat the effect of removing the calcium or in other words, forming a chromium salt instead of the calcium salt of the lignosulfonate. The addition of excess sodium dichromate, would also result in an excess of chromium salts formed by the reduction of the dichromate and would have somewhat the effect of the addition of an excess of chromium sulfate over that necessary to make the base exchange. This method of forming the salts, however, does not yield a product which is as effective for mud formulation as the methods previously described where calcium is removed, for example as the sulfate or otherwise, because calcium ions cause thickening of drilling mud and because of the miscellaneous reaction products. However, the effectiveness of agents made in this manner can be improved by removing the calcium during the treatment, for example, by adding sulfuric acid or any other acid whose anion forms insoluble salts with calcium or by addition of suitable salts which form insoluble compounds with calcium such as sodium sulfate. This illustration is mentioned by way of example that an improvement can be obtained by the presence of an excess of chromium, aluminum, copper, iron salts or combinations thereof, even though there is an equilibrium mixture present with other ions, such as potassium and sodium, but is not given to indicate a preferred method of operation.

It should be noted that an excess of sodium ions resulting from excess sodium dichromate addition is not seriously harmful since the drilling mud clays are also sodium salts and the additional sodium ions introduced into the mud by the additive are relatively few.

The iron, chromium, copper, and aluminum salts of the lignosulfonates thus formed are useful as drilling mud thinners in muds which do not contain an excess of lime, i.e., fresh water muds, and these products are thereby distinguished from the spent sulfite liquor products previously used as thinners in the so-called lime base muds. These previous lignosulfonate thinners which may be ammonium, sodium, magnesium, or calcium salts of lignosulfonates are operable only in the lime base muds and are not effective in muds which are sometimes termed fresh water muds, i.e., muds of low pH and which do not contain salts of aluminum, iron, copper and chromium the inclusion of said salts being a part of our invention and discovery. The aluminum, iron, copper, and chromium salts of the spent sulfite liquor on the other hand are effective in varying degrees over the whole pH range of the fresh water muds and are also operable as thinners in lime base muds.

Furthermore, let it be noted that another alternate pretreatment may be used whereby the hot spent sulfite liquor is acidified and air blown or treated to remove the sulfur dioxide and then oxidized with the agents described below. By this course the spent sulfite liquor is purified of sulfur dioxide and apparently the structure of the components of the spent sulfite liquor is modified and the oxidizing agents if later used are conserved for performing their special functions.

As heretofore indicated an important feature of our invention and discovery is that the oxidation of spent sulfite liquor components leads to increased activity or enhanced properties of said components respecting dispersing properties, and that these changed properties are manifested in the thinning of the viscosity of clay suspensions and also in the reduction of the gel-like properties of such suspensions. We have found that most oxidizing agents are operable in varying degrees as to the improvement produced. Particularly effective for this purpose are the following: hydrogen peroxide, ozone, lead dioxide, chromic acid, chlorine, alkali and alkaline earth hypochlorites, alkali metal chromate, alkali metal permanganate, alkali metal persulfate, alkali metal perborate, and electrolytic oxidation. These several agents are the preferred oxidizing agents.

The preferred forms of the oxidizing salts such as chromates, permanganates and persulfates are the sodium and potassium salts, but the ammonium salts may also be used and where available are included in the descriptive term alkali metal salts.

When chromate is used for oxidation of spent sulfite liquor, the chromate is added preferably as sodium dichromate, since this form is the most readily available in commerce, and in subsequent discussions the chromate addition is referred to as dichromate. However, it is well known that in aqueous solution chromate ions (CrO and dichromate ions (Cr O are readily interconvcrtible, depending on the pH of the solution. In strongly acid solution, the dichromate ion predominates, but on neutralization with alkali the dichromate shifts to the chromate. Equilibrium is readily reached between the two forms, depending on the pH of the solution. There fore the chromate may be added as either chromate or dichromate.

Further in regard to oxidation with chromium compounds: By experiment, we have discovered that oxidation of fermented spent sulfite liquor solids with sodium chromate at pH 8 provides a product which has substantially the same thinning effect on the drilling mud as a product obtained by oxidation with sodium dichromate at pH 4. In making this experiment both products were converted to the iron salt to make the mud test. Furthermore chromic acid may be used instead of the chromates in which case it is usually necessary to add sodium hydroxide to neutralize the product to about pH 4 to 5 prior to drying. All of these chemicals, i.e., sodium chromate, sodium dichromate and chromic acid give oxidized products, the iron, aluminum, copper and chromium salts of which are effective thinners for both lime and fresh Water muds and give substantially similar results.

One method of obtaining oxidation is by electrolysis whereby oxidation takes place at the anode of an electrolytic cell. We have found that effective electrolysis can be obtained in a simple cell with or without a mem brane to separate the anode and cathode, and improved products have been obtained with current usages from a desired effective amount up to about 5 ampere hours or more per gram of sulfonated lignin-containing material. It will be understood that the amount of impurities or contaminants, including carbohydrates and sulfur dioxide, in the sulfonated lignin-containing material electrolized, will change the electrical current consumption (i.e., ampere hours per gram of said sulfonated material) to obtain a given desired result. Thus we have found that from about 0.2 to 5.0 ampere hours per gram is suitable for fermented spent sulfite liquor but less current consumption will be necessary for more purified sulfonated material while greater current consumption may be necessary for less purified sulfonated lignin-containing material.

The electrolysis should be conducted under conditions which will bring about oxidation and not reduction. For this purpose a non-reactive anode, that is, an anode which does not dissolve substantially during the electrolysis, should be used. Thus platinum is suitable. Also, it is preferable to carry on the electrolytic oxidation prior to forming a lignosulfonate salt of the metal iron, aluminum, copper and chromium. However, if the salt is formed before electrolysis, any metal lost for example by plating on the cathode should be replaced, that is, the equivalent of such lost metal should be readded to the electrolyzed solution. This loss of metal ions may be substantially eliminated by electrolyzing under acid conditions of below about pH 3, or as stated above, by electrolyzing before forming the said salt.

Oxidation by addition of sodium perborate results in contamination of the product with sodium borate which must'be removed to obtain the greatest efiiciency of the product. One method of purifying the product is to remove the resulting borate ions as calcium borate which readily occurs if the starting material is a calcium salt of sulfonated lignin-containing material. The sodium perborate has an alkaline reaction and raises the alkalinity of the. solution sufliciently to make calcium borate insoluble. The calcium borate may be removed by filtering or settling. Other methods known to those skilled in the art can be used for such purification. As set forth herein, chlorination also results in by-products of the reaction which should be removed by purification to obtain more effective products for drilling mud thinning.

In regard to the choice and use of oxidizing agents for practicing our invention, two factors are of prime importance: The strength or power of the oxidizing agent and the quantity of oxidant being used in proportion to the organic solids being oxidized. The strength or intensity of the oxidizing agent is expressed as an oxidation-reduction potential, and tables of these potentials are available in the chemical literature. We have found that the oxidizing agents which are suitable for carrying out our invention have a range of oxidation potentials greater than 1.3. The quantity of oxidant which is used to bring about the desired result may be expressed as the weight in grams of each oxidant which can be used per 100 grams of sulfonated lignin-containing material.

The amount of oxidant required depends on the specific oxidant being used, the nature and purity of the sulfonated lignin-containing material being treated and the conditions under which the treatments are conducted. In general and for practical operation, particularly respecting cost, 1% to by weight of the several oxidants on the basis of the dry sulfonated lignin-containing material is all that is required to produce the desired result. However, when the oxidant is of a less concentrated character, as in the cases of alkali persulfate and perborates, both being costly, a large percentage of such oxidant is required to obtain the desired result. In any case, the reaction should be conducted in such a manner and with concentrations and proportions of the reactants so that gelation of the solution does not occur and a permanently soluble product is obtained. Solubility of our additive product is a fundamental requirement because the product is to be added to a drilling mud system, one component of which is water in which the additive product must dissolve to function as a thinner. Also, the dissolving brings about the distribution of the agent uniformly throughout the medium which increases the effectiveness of the product.

By way of explanation gels contain some occluded Water soluble product and to the extent that the water soluble component is available or the gel dissolved in the medium said gels function somewhat as thinners. If any thinning action occurs with gelled (i.e. insoluble) products, such thinning is deemed not to be due to the gel functioning as a surface active agent but is due to the soluble component accompanying the gel. At higher pH, i.e., about 9, the unwashed gelled products dissolve to some degree and show some tendency to thin the mud. Particularly is this true if the dissolved component is not washed out. In any case gels are not desirable because the material is less eflicient.

Permanently stable solutions without gelation as shown in the examples may be obtained by conditions which slow the rate of reaction and keep the reactants in low concentration in relation to each other. Furthermore, other conditions affecting the formation of gels in more or less degree are the degree of sulfonation, the concentration of the sulfonated lignin containing material, temperature, concentration of the oxidant, pH and effectiveness of mixing. In addition, the character of the sulfonated lignin containing material being treated affects the amount of oxidant being used, in particular, the degree to which the materials have been previously purified, especially of reducing substance such as sulfur dioxide and carbohydrates, and/or fractionated. The degree of s-ulfonation is important in regard to water solubility. Also, we have discovered that the molecular weight, and apparently the molecular weight distribution within the fraction will affect the quantity of oxidant required to bring about the desired result. By way of example and not limitation, when a 45% to 50% solution concentration of fermented spent sulfite liquor solids is being used as much as 15% or more of hydrogen peroxide may be added, whereas, with potassium permanganate or potas sium dichromate, such concentration of spent sulfite liquor thickens rapidly to a gel when about 10% of these agents is added. Furthermore, by way of example to show the effect that the prior history or character of the spent sulfite liquor has on the quantity of oxidant which may be used without causing gelation, when a caustic treated fermented spent sulfite liquor is used at pH 4, about 8% of sodium dichromate will cause gelation at 42% total fermented spent sulfite liquor solids, 15% of sodium dichromate will cause gelling at 25% solids and 21% of sodium dichromate at 12% total solids, the dichromate in each case being added as a 25 solution in water at C. Let it be noted that the above percentages are based on the weight of the dried fermented spent sulfite liquor solids being treated. Moreover under other conditions, even more of this oxidant can be added without causing permanent gelation or loss of Water solubility.

Purification and molecular weight are other factors which bring about gelation with different proportions of the oxidant. For example, using a solution of 45% to 50% total solids, about 4% by weight of the solids of the oxidant will gel the purified high molecular weight lignosulfonates at a pH of less than 4.5, whereas, as much as 8% or more of potassium permanganate or sodium dichromate may be added to the low molecular weight lignosulfonate fractions of the same concentration without gelation. But substantially larger concentrations of sodium or potassium dichromate may be added if the reactants are dilute. For example, a low molecular weight lignosulfonate fraction (40% of the total original fermented spent sulfite liquor solids) containing 17% of reducing substances expressed as glucose as a 2.5% solution in water treated at room temperature with 50% by weight of sodium dichromate as a 2.5% solution at a pH of 3 yielded after drying at room temperature a product which was slowly soluble in water. With 40% by weight of sodium dichromate the product was rapidly soluble in water. During such reactions the pH rises and acid such as sulfuric may be added to maintain the desired pH. The reaction under the above conditions was substantially complete in one hour. Thus the objective, namely a water soluble oxidized product, can be obtained with up to 50% by weight of the dichromate oxidant depending on the conditions used in the reaction. Similar results are obtained with potassium and sodium permanganate. The other oxidants which are less subject to providing insoluble products may also be used up to 50% and more by weight of the sulfonated lignin-containing material depending upon said conditions.

PILOT TESTS We have discovered that the oxidants which are suitable for oxidizing the sulfonated lignin-containing material may be roughly divided into two groups: Those containing the metal ions chromium and manganese, i.e., the alkali metal chromates and the alkali metal permanganates and those involving gaseous oxidation components, such as hydrogen peroxide, sodium persulfate, sodium perborate and chlorine and, accordingly, different tests were originally necessary in establishing the maximum amount of the oxidant which could be used for any particular sulfonated lignin-containing material.

The maximum amount of oxidant particularly the chromates and permanganates which can be used with any one sulfonated lignin containing material can be determined by the following pilot test. A dissolved sample of the sulfonated lignin containing material is diluted to 2.5% solids, acidified to pH 3.0 with sulfuric acid for this particular est and various amounts of sodium dichromate added, together with sulfuric acid to maintain pH 3.0. The solutions are then allowed to stand about 1 hour at room temperature, adding sulfuric acid at intervals to maintain pH 3.0. At the end of 1 hour, the sample is heated to 80 to 90 C. and digested at this temperature for about an hour. The product samples are then dried at 60 C. and tested for solubility in water. The highest amount of dichromate giving a soluble product is the maximum limit of the amount of oxidant than can be used.

Another guiding test as to the maximum quantity of oxidant wich may be used with any one sulfonated lignin containing material in forming the products of our invention and discovery is an evaluation of the performance of the product as a thinning agent for drilling mud. To apply this test, a solution of about 10 grams of sulfonated iignin containing material dissolved in 10 cc. of Water is treated with 2 grams of ferric sulfate to convert the lignosulfonate to the iron salt, the solution heated to 80 C. and centrifuged to remove calcium sulfate. This solution is then treated with various amounts of the oxidant being tested at a pH of about 3 to 5 for this particular experiment and heated at 8090 C. for about 1 hour and 16 then dried at 60 C. The product is tested for solubility in water, as above, and then for m-ud thinning properties as described herein. If the properties of the base mud are not improved by the addition of the product, then too high a concentration of the particular oxidant was used in the oxidation stage.

In using the oxidizing agents which evolve a gas in the oxidation process, such as hydrogen peroxide, chlorine or sodium persulfate, a greater amount than that equivalent to sodium dichromate or sodium permanganate is required, since the use of such agents involves a more rapid deterioration and possible excapement of gas without complete reaction. It is probably also that the polyvalent metals manganese and chromium contribute to the effectiveness of the final product and these are not present in said other oxidants. Therefore, while the equivalent proportions are a guide to the relative amount of oxygen that can be used, they are not exactly equivalent in regard to the improvement which equivalent amounts of each of the oxidants will produce in the product.

Optimum thinning properties appear to be attained with sodium dichromate usages which give solutions well removed from the point of gelation. For a fermented spent sulfite liquor, of 40% to 45% total solids, the preferred amount of oxidant is about 7% to 9% of sodium dichromate based on the spent sulfite liquor solids for overall performance respecting the several properties required in drilling mud, but especially low water loss characteristics have been observed with about 18% of sodium dichromate. On the other hand, with chlorine which is considered an oxidizing agent herein, substantially more than the other agents can be added because some of the chlorine reacts by substitution with the spent sulfite liquor components, so that additional chlorine is required to bring about the desired oxidation results.

The time and temperature of the reaction is important in that the reaction should be allowed to go essentially to completion and the product should be substantially free of gels. It is preferable that the oxidation be controlled to yield a solution which can be dried to a powder which can he redissolved in water. If the oxidation is too severe the solution may gel or the dried solids may not be water soluble. Potassium permanganate and potassium dichromate are very rapid in their action and usually the oxidation is complete in 5 to 20 minutes and thereafter the solution is stable and shows no visible evidence of change on standing. If 10% of these agents are added as a 25% solution to concentrated liquor of greater than 40%, the spent sulfite liquor will gel in 15 minutes at room temeparture, or if the solution is hot, the gelation will occur almost immediately. Solutions more dilute in organic solids, permit the addition of higher percentages of these oxidants. With milder oxidants, such as hydrogen peroxide, 15 minutes to 24 hours are necessary to bring about the completion of the oxidation. The temperature is usually a matter of choice and convenience but should be such that the reaction is complete in the time provided, although lIO WGI temperature will give less difiioulty with local formation of gels.

The concentration of the spent sulfite liquor can be any concentration up to 70% by Weight of solids, but it is desirable to have the concentration of the liquor low enough to promote homogeneous reaction and prevent subsequent gelation. However, for practical reasons, it is preferred to use solutions of as high concentration as possible and, preferably, of the order of 40 to 50% solids concentration. For this reason, the dilute solution of the oxidant is added to the cool spent sulfite liquor solution of 40 to 50% solids with intensive mixing and after the reaction has been more or less completed, the solution is heated to the temperature at which drying will be conducted.

Thus, it is clear that, because of the choice of oxidants involved in providing required properties, the varied nature of the sulfonated lignin containing material, and the many factors involved in the physical conditions under which the reactions can be conducted, and also the many well known types of equipment used in mixing the reactants, that it is not feasible to set forth the exact operating conditions for each product of production. Furthermore, the factor of what mud property is most desired must be considered since the properties do not respond in a parallel man-ner to all treatments. That is, sometimes all the properites may be improved whereas in some cases only one of the properties may be improved. Accordingly, a selection must be made to obtain the de sired result. But many examples are given in the herein disclosure which will enable persons skilled in the art to select conditions of treatment best suited to the particular requirement of the case in hand. But for most cases for use in the field the oxidants can be used in the concentration of 1 to 50% by Weight of the organic solids as herein disclosed and thereby obtain a fully reacted and soluble product without gelation. The determination of the maximum amount of any given oxidant which can be used for any particular sulfonated lignincontaining material is determined by pilot tests as hereinbefore described. But the usage is one depending upon which mud property is most desired.

Special processing is necessary when chlorine is used as the oxidizing agent since in addition to oxidation and any other reactions which occur, there is a reaction of chlorine with the sulfite liquor components, and there are by-products from the reaction such as hydrochloric acid, which if left in the product may have a deleterious effect. For example, it has been found that on the addition of 1% to 4% of chlorine on the basis of the dry weight of the spent sulfite liquor solids, the properties of the sulfite liquor residue improve even without further purification to remove the end products formed, such as calcium chloride. The chlorination can be increased up to the addition of 45% of chlorine above which the chlorinated lignin tends to become insoluble in the strong hydrochloric acid and calcium chloride solution formed in which case it is necessary to further refine the products by removing the hydrochloric acid and reaction products. One of the best methods of accomplishing this purpose is to precipitate the chlorinated lignin with lime. This treatment has additional benefit of purifying the lignosulfonates not only of the hydrochloric acid and its end products, but also of the carbohydrates themselves. In this connection we have discovered that, whereas with regular spent sulfite liquor it is difficult to divide the lignosulfonates into several fractions by treatment with lime, surprisingly with the chlorinated lignins of our invention and discovery, the products can be divided very readily into fractions of different average molecular weight. This finding has been of extreme usefulness in the preparation of specific fractions of the chlorinated lignin as to molecular weight.

It has been known that lignosulfonates may be precipitated in mass from spent sulfite liquor by adding at one time relatively large quantities of lime slurry until a pH of 11-12 is reached. It is our discovery that the lignosulfonate can be precipitated and recovered as fractions of different molecular weights by adding the lime in small increments. Especially surprising and useful is our discovery that if the lignosulfonates are treated with chlorine then they may be more readily divided by lime precipitation into many small fractions, while at the same time purifying the lignosulfonates from the carbohydrates, chlorides, and other miscellaneous components of the sulfite liquor. The oxidized and chlorinated lignosulfonates, fractionated as to molecular weight by lime, may then be used as such as lime base mud thinners, or they may be converted to aluminum, iron, copper, and chromium salts and as such they also make highly effective fresh water drilling mud thinners. Such oxidized and chlorinated lignosulfonates may be converted to other salts such as sodium, magnesium, ammonium, etc., if calcium is objectionable in the product. Fractionation of the chlorinated spent sulfite liquor can also be accomplished by the alcohol fractionation process according to the disclosures of our application Serial No. 437,833.

In summary, our invention comprehends the discovery that oxidation with or without forming a salt of a metal selected from the group of iron, aluminum, copper and chromium of the lignin sulfonate-containing material provides an improved drilling fluid, and that the amount of oxidation can be greatly varied.

The oxidized products are useful as thinners, and this is particularly important because products can be prepared from the original spent sulfite liquor merely by a simple oxidation process to give products equivalent as thinners to those prepared by more complex and expensive procedures. Furthermore, let it be particularly noted, essentially in precipitation and fractionation procedures only a part of the spent sulfite liquor solids are available for use as mud thinners while, in contrast, our invention and discovery makes use of substantially all of such solids. This point is important where yield and costs are of prime consideration.

In general, the products of our invention and discovery may be prepared from spent pulping liquor and the solids therein in the condition as received directly from the digester, or said products may be prepared from modifica tions of the said solid components of the spent pulping liquor. Such modifications may be provided by various treatments but, nevertheless, the resulting solids still do constitute soluble sulfonated lignin-containing materials. By way of example and not limitation the treated solids may be as follows: They may beas they exist after fermentation of spent sulfite liquor whereby the carbohydrate content is reduced or they may be as solids after hot spent sulfite liquor is acidified and air blown; or they may be obtained as set forth in US. application Ser. No. 391,116, which briefly states the spent sulfite liquor treated with an inorganic base, for example sodium hydroxide, in developing a final pH of 7-10, the same may be heated at 40 to C. for a period of 30 minutes to 2 weeks, the solid organic components being maintained in solution throughout the said reaction period; or the spent sulfite liquor may be essentially freed of carbohydrates and extraneous material by any one of a number of procedures, preferably by fermentation or by adding increments of lime, or by precipitation, dialysis, separation by organic solvents, and/or organic bases, or precipitated as basic lignosulfonate for example with lime, or by salting out with salts such as calcium or sodium chloride.

Furthermore, the spent sulfite liquor components may have been derived by the pulping with agents other than the usual magnesium, sodium, ammonium, and calcium bisul fites. These other agents disclosed herein are iron and aluminum bisulfites.

Oxidation treatment improves the spent sulfite liquor components in providing a more effective lime mud thinner or more elfective thinning and dispersing action in general, i.e., in both lime base and fresh water muds.

Base exchange to form iron, aluminum, chromium, or copper salts enhances fresh water mud thinning properties, and improves some of the lime mud properties, as for example a base exchange with aluminum sulfate will yield a product with lower viscosity and gel characteristics in lime mud.

Up to this point the disclosure has dealt primarily and especially with the treatment of the spent sulfite liquor components and with their fractionation, their treatment with metallic salts, and the oxidation of said components, as well as with the use of such spent sulfite liquor components in preparing well drilling muds in general, in establishing or proving first, that a change is made in said components by the treatment of our invention and discovery, and, second, that the magnitude of the change is surprisingly great, as evidenced by the increased and augmented effectiveness of the treated components as revealed in the preparation of such drilling muds.

Now the disclosure will relate more specifically to the particular use of the said components in providing a product for controlling the colloidal and physical properties of gypsum base drilling muds so as to maintain them in the most desirable condition for use.

As one application of our invention we provide for muds where contamination is encountered from calcium sulfate (either as so-called gyp, or in the anhydrite form, Portland cement) and similar calcium bearing material which would supply calcium ions which fiocculate sodium bentonite as calcium bentonite through base exchange reaction. This flocculation of the bentonite results in an increase in the mud water loss. The water loss value of the drilling fluid may be 8 cc. at the time of entering a massive anhydrite section and 24 hours later be anywhere from 25 to 75 cc. if the mud is not treated properly. Anhydrite and cement differ in that the former supplies the sulfate radical along with the calcium while the latter supplies the hydroxyal radical which increases the fluid pH. The sulfate radical does not affect the pH of the solution although the pH of the mud may drop slightly through replacement of the hydrogen ions from the bentonite particle by the calcium. The net effect of the drilling of sufficient anhydrite to saturate the mud aqueous phase with calcium is first to result in a marked increase of gel strength followed by a gradual increase in the water loss as the bentonite is converted to the calcium bentonite. As the calcium bentonite flocculates through loss of hydration properties, the gel strength decreases. The final result is a mud of high water loss, low viscosity and low gel strength (p. 25, Composition and Properties of Oil Well Drilling Muds, Rogers, Rev. Ed.).

In case of contamination with calcium bearing strata, Rogers further states (beginning on p. 379 of said text):

The precipitation and removal of calcium from solution can be accomplished by at least four chemicals. These are:

(1) Bentonite.

(2) Soda ash (Na CO (3) Disodium phosphate (Na HPO (4) Barium carbonate (BaCO The first, the use of bentonite, is not very efficient but has been used in drilling anhydrite together with large quantities of thinners. It is not recommended for large quantities of calcium sulfate and will not be discussed further.

Soda ash is a common chemical precipitant for calcium sulfate. The reaction is:

In this reaction the calcium is precipitated as calcium carbonate while soluble sodium sulfate is formed and remains in solution. In this reaction 1.0 pound of soda ash will precipitate 1.283 pounds of calcium sulfate. The reaction goes to completion and excess quantities of soda ash are not required. The method has two disadvantages. The first results from high pH of soda ash. The compound in strong solution has a pH of approximately 11.2. The action of high pH in gelling bentonite mixtures has been shown previously. Since the pH of the mud will increase greatly from excess soda ash it is usually customary to use SAPP as a thinner because of its low pH value. The second disadvantage results from the continuing accumulation of sodium sulfate as calcium carbonate is precipitated. Any increase in concentration of such soluble salts acts to increase the gel strength. One of the main difiiculties with the soda ash treatment where thick beds of anhydrite are encountered is that the development of high gel strength from increased mud pH and sodium sulfate formation is so extensive that soda ash additions have to lag additions of thinner to reduce the mud pH and gel strength. As a result the calcium contamination continues to gain and the fluid loss continues to rise. It has been found impossible to maintain fluid-loss values below 15 cc. when using this treating method to drill massive anhydrite. Where the contamination consists of stringers of short duration, soda ash can be used to handle anhydrite satisfactorily as its extent is not sufficient to allow accumulation of sodium sulfate or the high pH condition.

Disodium phosphate as a chemical precipitant for calcium sulfate is similar in many respects to soda ash. The reaction with anhydrite is:

The products of the reaction are calcium phosphate, which precipitates from solution, and sodium sulfate and sulfuric acid which remain behind as soluble constituents. In this reaction 1.0 pound of disodium phosphate will precipitate 1.430 pounds of calcium sulfate. While disodium phosphate is slightly more efficient, pound for pound, as a precipitant for calcium sulfate than is soda ash, its greater cost is a deterrent to its use for this purpose. The similarity with soda ash results from the single precipitation of the calcium with sodium sulfate as a residue. The divergence is largely in the pH difference of the two compounds. Disodium phosphate has a pH in strong aqueous solution of 8.6. The addition of this mildly alkaline compound to the mud does not result in as high gel strengths as obtained from soda ash. The residual quantities of sodium sulfate and acid act to increase the viscosity and gel strength of the mud. There are no data in the literature covering case histories of massive anhydrite drilled with this compound.

Barium carbonate makes a satisfactory chemical precipitant when drilling massive anhydrite. The reaction is:

CaSO +BaCO +CaCOg+BaSO In some respects this treatment is superior to that of soda ash or disodium phosphate. This results from the complete precipitation of both the calcium and the sulfate radicals of the anhydrite as well as the barium and the carbonate of the treatment, leaving no soluble salts in solution. The barium carbonate is approximately neutral in pH and allows the mud to be restored to its original condition and allows lot fluid losses and visoosities to be maintained While drilling anhydrite. The principal disadvantage of the method lies in the large quantities of material required and the resulting high cost. 1.0 pound of barium carbonate will precipitate only 0.691 pound of calcium sulfate. In addition, the reaction is not very efficient as more barium carbonate must be used than called for by the reaction. Fortunately the addition of excess quantities of barium carbonate does not affect the mud adversely and over-treatment is primarily undesirable because of the cost of the barium carbonate so wasted.

Thus, all these methods of overcoming the contaminant calcium sulfate fail, or are objectionable for one reason or another.

By way of summary, it may be stated that presently three methods of treatment are commonly used in the field to overcome the deleterious effect of calcium sulfate:

(1) One method is to convert the mud to a limed mud by adding 3 to 5 pounds per barrel (a barrel being about 400 pounds) of hydrated lime, 1% pounds per barrel of tannin, or 2%. to 3 /2 pounds per barrel of calcium lignosulfonate and then adding carboxymethyl cellulose and starch to control water loss. This method is expensive.

(2) Another method used is the employment of high pH red mud. The mud is raised to about pH 12 with equal parts of caustic and tannin, and water loss is controlled by addition of carboxymethyl cellulose. This method is also objectionable because it is expensive.

(3) A third method, and probably the most commonly used, is to convert to a gypsum base mud by adding 3 to 4 pounds gypsum per barrel of mud. The mud is thinned to the desired viscosity with water, and 4 to 6 pounds per barrel of starch added to reduce water loss, and A to /2 pound per barrel of a preservative added to prevent fermentation of the starch. This mud is objectionable because of the high flat gels which made the mud hard to pump in deep wells and make it difficult for cuttings to separate in the surface mud pits. Furthermore, by adding water, the volume of the mud is increased, and therefore part of the mud must be discarded to accommodate the capacity of the equipment. Also, because of the addition of water, the density of the mud is decreased and additional expensive weighting material must be added to increase the weight of the mud for deep drilling.

One of the outstanding features of using the product of our invention and discovery in preparing drilling muds is to provide a method of controlling mud properties against contaminants in drilling calcium sulfate bearing strata which is less expensive and requires a minimum of effect and attention at the time such a stratum is encountered in the drilling, or when contamination by such contaminants is anticipated.

A further outstanding feature of the use of the product of our invention is the providing of a gypsum base mud with a low gel ratethat is, mud with a low initial gel strength so that cuttings will settle out and be removed while the mud is flowing to and circulating in the mud pit, but with a sufficiently high gel strength in the quiescent state so that sand and cuttings will not settle out in the well if drilling operations are temporarily interrupted for a period of time. Heretofore, gypsum base muds in common use have had high flat gels, that is, high initial and final gels. The viscosity of these muds increased as sand and fine cuttings accumulated, and it was necessary to maintain low viscosity by discarding some of the mud and bringing the remainder up to volume with water and bentonite. This treatment raised the water loss and it was necessary to add starch and carboxymethyl cellulose, which are expensive, to maintain a low water loss. By using a mud as in this invention, with a low initial gel strength without watering-back, that is, the addition of more water, the cuttings nevertheless do settle out in the mud pit, and also the maintenance cost of replacing discarded mud is eliminated.

In other words or by way of summary, the gypsum base muds utilizing the sulfonated lignin containing additives of our invention and discovery constitute a new drilling mud system of our invention and discovery. Heretofore, calcium sulfate contamination was eliminated by chemical means or the contaminated mud was discarded and new mud substituted. In combination with the additives of our invention calcium sulfate saturated muds, i.e., gypsum base muds, have very desirable drilling mud properties and also the high calcium ion content of these muds is effective in reducing the hydration of certain shales encountered in oil well drilling. This prevents the shales from swelling and closing the bore hole and the shale cuttings from making an excessive amount of thick mud.

Another desirable feature of our gypsum base muds is their thermal stability, a property essential for drilling deep wells in which high temperatures are encountered. These muds of our invention are characterized by their thermal stability at deep well temperatures.

A further important feature of the use of our products or additives is found in providing a mud resistant to gypsum contamination, which may be converted to an oil emulsion mud.

Still another outstanding characteristic of the use of the products or additives of our invention and discovery is found in the providing generally of muds with good thermal stability for drilling deep wells where high temperatures are encountered. Temperatures can very seriously affect the necessary properties of the drilling mud, and therefore it is a very important property of the prod- 22 uct and process of this application to provide thermal stability.

The treatment of the drilling mud according to our invention and discovery to control calcium sulfate contamination comprises adding a lignosulfonate thinner or additive which may be derived for example from spent sulfite liquor as hereinabove described, combined with sodium sulfate, said combination being formed in proportions of 1% to by weight of the sodium sulfate based on the said spent sulfite liquor solids, the most advantageous proportion being determined by a pilot test to determine about the proportion necessary to meet the particular situation developed by the drilling. In place of sodium sulfate, other salts such as iron sulfate, aluminum sulfate, sodium sulfite, potassium sodium tartrate, sodium oxalate, sodium phosphate, sodium carbonate, sodium bicarbonate, and their corresponding potassium compounds, i.e., potassium sulfate, potassium sulfite, potassium oxalate, potassium phosphate, potassium carbonate, potassium bicarbonate and mixtures thereof, may be used. All of these compounds react with dissolved calcium sulfate to precipitate calcium salts less soluble than calcium sulfate and produce soluble sulfates. The latter through common i-on effect further reduces the solubility of calcium sulfate and hence decreases the calcium ion concentration. In many muds it is desirable to maintain low calcium ion concentration to avoid clay flocculation. Regarding the use of bentonite clays, Rogers states, on page 378 of his text quoted above:

Sodium bentonite is a highly hydrated, dispersed and ionized member of the bentonite salts and possesses good fluid-loss reducing properties. Calcium bentonite, on the other hand, is poorly hydrated and dispersed and tends to fiocculate. This flocculation results in fewer but larger particles which tend to precipitate. As the calcium bentonite forms in increasingly greater percentage the agglomeration of the particles and precipitation result in a decreased viscosity and gel strengths and increased fluid loss properties. The formation of calcium bentonite results in depletion of calcium in the aqueous phase unless replaced by further solution of the contaminants.

Parentheti cally, be it particularly noted, that the conditions of the various strata encountered in the drilling of oil and gas wells are so complex and vary so much and vary from area to area that a pilot test should be made to determine what amount of the product or addi tive of our invention and discovery is effective and what amount is most efficient as is commonly done in the drilling operations for conditioning the particular mud for the particular well being drilled. Such testing commonly continues as the drilling proceeds.

In regard to making the salt of the sulfonated lignin by base exchange, any or all of the sulfonated lignin may be converted and the efficiency of the resultant product will depend on the degree of conversion. As hereinbefore stated, the calcium, magnesium, ammonium or sodium base lignosulfonates are effective in lime base muds but not effective in thinning fresh water muds. On the other hand, the lignosulfonate salts of iron, aluminum, copper and chromium do thin the fresh water muds. Hence, it is necessary to convert the former salts to the latter and the proportion of conversion determines the efficiency. Thus, an effective amount of conversion would be an amount of conversion to the latter salts which would in a pilot test in a mud show a noticeable thinning of the mud. By way of example but not limitation, it the salt were fully converted then even the addition of a quarter of a pound per barrel of the converted salt would show thinning whereas if say only 10% of the sulfonated salt were converted then it would require adding a quantity of the product on the order of several pounds per barrel to show thinning.

The amount or concentration of the additives of our invention and discovery which can be added to drilling fluids by way of conditioning these fluids to the desired properties will depend on such factors as the nature of the mud to be treated and the contaminants therein or to be encountered, the characteristics desired in the mud, and the degree of purity of the additive and the specific agents used in preparing and formulating the additive according to our disclosure. For practical purposes, usages of the order of one-quarter of a pound to thirty pounds per barrel are preferred. It is one of the advantagcs of our additives that they do not show the thickening of a mud at low usage that is experienced in the use of quebracho for thinning drilling mud, which thickening is referred to as over treatment. In fact, in the use of quebracho special attention is required to eliminate the danger of over treatment, which often occurs around 4 to 6 pounds of quebracho per barrel of mud. With the additive of our invention, prepared from a fermented spent sulfite liquor oxidized with sodium dichromate and converted to the iron salt, for example, the danger of over treatment is avoided since thickening does not occur below to pounds per barrel. Furthermore, decreases in water loss are observed with usages up to 50 to 100 pounds or more per barrel, particularly in gypsum and salt water drilling fluid with only slight thickening. Such amounts of additive are used in taking full advantage of our invention and discovery. The above emphasizes the universality character of our invention and discovery in the area of permissible amounts to be employed without adverse action. Thus it is a particular advantage of the additive of our invention that water loss values as low as 1 or 2 cc. may be obtained with high usage of the additive without as much thickening in many cases as would occur if water loss Were reduced by addition of carboxyrnethyl cellulose or like water loss reducers which have a substantial thickening effect on drilling mud. Furthermore, when starch is used for water loss control, it has the definite disadvantage of deterioration by microbiological action to which our additives are very resistant. All of which is of practical importance to the well drilling crew. Oxidized lignosulfonates without conversion to salts of iron, aluminum, copper and chromium as well as the unoxidized lignosulfonate salts of these metals can be added in the same concentration range to drilling mud for effective thinning and water loss control.

2% sulfite liquor provides for selection of fractions to yield desired properties in the additive formulated as disclosed herein.

Thus, to follow through in detail, the starting material may be, as previously discussed, either the spent sulfite liquor solids as contained in the spent liquor as received from the blow pit, or these solids refined in various manners, such as by fermentation, lime precipitation, fractionation, etc. In any case, the solids to be treated are preferably concentrated to 30% to solution. One method of operation, following from point (1) on the chart, is to treat the concentrated liquor with an acid and heat for example for 1 to 2 hours at 95 to 100 C. At this point if calcium sulfate is precipitated, it may be separated, depending on the purity desired in the final product. Said acid treatment may be carried out at less than about pH 4 at temperatures from 50 C. to 180 C. as more fully set forth in our co-pending application Ser. No. 723,036 (U.S.).

This product can be neutralized with a base such as sodium hydroxide (we mean a compound which yields hydroxyl ions in solution) to a pH above 3.5 so that it can be dried without degradation and then used as such as a limed mud thinner (2) without further treatment; or it can be further improved by oxidation, preferably with an alkaline reagent such as potassium permanganate or sodium dichromate as indicated at point (3) in the outline. Either product may be used as a liquid, or it can be reduced to solids by evaporation and drying. In either case, these products may be used as thinners for drilling muds. Alternatively, the product can be converted to the salt (3a) of iron, chormium, copper, and aluminum, and this is outstanding in the fact that the thinning action is improved for both fresh water and lime base muds.

Again, the acid treatment may be carried out with an acid salt such as ferric sulfate, aluminum sulfate, chromium sulfate, or copper sulfate in such proportions as to also effect a base exchange (4) and yield a product which is effective for thinning all types of water base drilling mud. This product may also be oxidized (4a) to obtain further improvement in mud thinning properties.

[Spent sulfite liquor from blow pit and with optional treatment fermented and/0r purified and/or fractionated and/or concentrated to 20%70% solids (or preferably concentrated to 30%-50% solids)] Salt (3a) Al, Cr, Fe, Cu

mud thinner or Fe Cu Cr Oxidize (9) lime Al salt (10) Alkalne (7) (see appl. S.N. 694,737)

Alum or Ferric Sulfate Oxidize (l2) Fractionate Manifestly, if the starting material was either raw spent sulfite liquor as it comes from the blow pit or if it was fermented spent sulfite liquor without further purification or fractionation, then any of the products of our invention as set forth in the above outline of the possible manifold treatments within our invention, may be further purified or fractionated by adding small increments of lime as herein disclosed or by solvent fractionation, application Ser. No. 437,833, filed June 18, 1954. and now abandoned in favor of US. Serial No. 703,664. Let it be noted that fractionation of the spent Rather than treating with an acid as in (1), the concentrated liquor may be treated directly with an oxidizing agent as in (5). In this case some of the oxidizing agent s required to oxidize the sulfur dioxide which escapes in the case of acid treatment. This oxidized product may be used as a mud thinner, particularly as a lime base mud thinner, or it may be converted to the iron, aluminum, copper, or chromium salt as in (6) whereby the properties are unexpectedly enhanced for thinning both lime base and fresh water muds.

Another pretreatment, which gives improvements in the sulfonated lignin-containing material preparatory to following the procedures of our invention, is the heating of the solution of the sulfonated lignin-containing material in Water solution at highly elevated temperature and at a pH greater than 4 and preferably about 7 to 10. The heating is carried out for a short'period of time above a temperature of 170 C. and of the order of 30 minutes at a temperature of about 200 C. At 220 C. the lignosulfonate becomes partially insoluble in water and gel-like and is not suitable for further use for the purpose of making drilling mud thinners. This heating is conducted while blowing the solution with a gaseous medium such as air or nitrogen. Products prepared in this manner have improved properties, said improvement in properties being somewhat equivalent to those attained by our process of acid treatment as described in our US. Ser. No. 723,036.

Another and highly effective procedure is to follow the process outlined in our application Ser. No. 694,737 involving treatment with alkali. This product (7) may then be acidified either with an acid (8) and oxidized (9), whereby a drilling mud thinner particularly effective for lime base muds is obtained, or further processed to form the aluminum, iron, copper and chromium salt (10). Instead of acid, aluminum, iron, copper, and chromium sulfate may be used through which an economical and effective spent sulfite liquor additive (11) is produced, the properties of which may be greatly enhanced by oxidation with any of the oxidizing agents previously mentioned, to yield (12) an extremely efiective agent for conditioning all types of water base drilling fluids, such as, fresh water, lime base, gypsum and oil emulsion types.

NB. We have discovered that spent sulfite liquor components, or such components chemicallyt modified in their separation from spent sulfite liquor, or in their preparation (i.e., we find that materials identified in general as lignosultonates respond favorably to our treatment) are greatly improved in their effectiveness as dispersing agents and for use in drilling muds by treating them with one or both of the following steps:

(1) Oxidizing said spent sulfite liquor components.

(2) Treating to form a salt having an element selected from the group consisting of iron, aluminum, chromium, and copper.

The order of the above steps or treatment (oxidizing or forming a salt) is immaterial.

Continuing our treatment against contamination by calcium sulfates, the product resulting from both steps 1 and 2, or the product of step 2, is treated with a salt in the proportion of 1% to 100% of the lignosulfonate Solids of said spent sulfite liquor solids, selected from the group consisting of sodium sulfate, sodium sulfite, potassium sodium tartrate, sodium oxalate, sodium phosphate, sodium carbonate, sodium bicarbonate, aluminum sulfate, iron sulfate, and their corresponding potassium compounds and mixture thereof.

Method of testingfi pecific examples of treatment, together with tables showing results of tests of the materials, will now be set forth. The method of making the tests is that commonly followed in the drilling industry.

The sulfonated lignin additives of our invention may be used in many ways, but chief among these is that revealed in drilling muds. For this purpose a material is required which will bring about a lowering in viscosity of the complex clay suspension which is termed the drilling mud, and will also serve to decrease its gel strength and Water loss characteristics. The accepted methods for evaluating materials to ascertain their utility for drilling muds are described in the publication entitled American Petroleum Institute Code 29, third edition, May 1950-- Recommended practice on standard field procedure for testing drilling fluids. This manual is prepared and published by the American Petroleum Institute, Division of 26 Production, Dallas, Texas, and is used throughout the industry for testing drilling muds.

In making the laboratory tests on drilling muds according to the procedures mentioned above, it is necessary to use a clay or combination of clays. In general, clays are of extremely wide distribution in the earths surface and are complex and difficult to define chemically. For example, H. A. Ambrose, Ph.D. and A. G. Loomis, Ph.-D., state regarding drilling mud clays: analysis tells us little with respect to the properties required in drilling. There has been no correlation between chemical analysis and clays and their suitability for drilling purposes, (The Science of Petroleum, volume I, page 458, 1938, Oxford University Press (London)). Although clays have been divided into several classes according to their chemical and physical form, the materials encountered or used in drilling muds are mixtures of said clays and so it has become practically accepted to define these materials in terms of what is termed yield value. According to practice then (Principles of Drilling Mud Control, 8th edition, pages 2 and 3, published by the American Association of Oil Well Drilling Contractors, Dallas, 1951), clays are defined in terms of yield value, which is the number of barrels of 15 cp. mud that can be prepared from a ton of material along with water. Thus in the examples, we refer to the use of natural clay and define the yield value to characterize the type of clay which would give similar results.

By following the standard methods identified above and using clays of defined yield value, the efiicacy of the sulfonated lignin additives of our invention is measured in terms of initial gel strength, viscosity, ten-minute gel strength, and water loss.

The Stormer viscometer has been used almost universally in making viscosity measurements according to the standard methods of the American Petroleum Institute. Also let it be noted that another means of measuring viscosity is a motor driven rotational viscometer known as the Fann VG meter (viscosity-gel). This instrument measures two factors of viscosity called yield value of fluids and plastic viscosity which are so related that two times the plastic viscosity plus the yield value is proportional to the viscosity at 600 rpm. Since the plastic viscosity is essentially constant for any one mud, the variation of the yield values indicate directly the variation of viscosity and therefore the yield value is reported in the tables where the measurements were made with the Fann instrument.

Generally only the yield value of the drilling mud is affected by the addition of thinners. Yield values are reducd by drilling mud thinners but plastic viscosity is affected very little. The plastic viscosity can only be changed by adding to or removing water from the mud. The Fann VG meter type of instrument is preferred for drilling muds since it indicates whether thinners are needed to lower yield or whether water is needed to decrease plastic viscosity.

The viscosity factor yield value of fluids defined above should not be confused with yield value of a clay which has been defined hereinabove as the number of barrells of 15 cp. mud that can be prepared from a ton of clay along with water.

Mud test pr0cedures.The following mud test pr cedures describe in detail the mud preparation and testing procedures used.

Lime m'ud test procedure.Sixty grams of a commercial rotary drilling clay with a yield Value of 45 barrels of 15 centipoise mud per ton of clay were mixed with 325 milliliters of distilled water in a Hamilton Beach No. 30 Drinkmaster mixer for 15 minutes at 15,000 rpm, and then aged by rolling, i.e., agitating in pint bottles overnight at room temperature. The aged mud was broken over to a limed mud by adding 6 grams of calcium hydroxide, 6 milliliters of sodium hydroxide solution containing 0.25 gram sodium hydroxide per milliliter, and the sulfonated lignin containing material additive to be tested (each gram added equivalent to 1 pound per barrel) and mixing for 5 minutes at high speed. Broken over is a term used in the industry to denote the procedure and the accompanying change in properties which occur when an excess of calcium hydroxide and sodium hydroxide is added to a clay with intimate mixing as next above set forth. The mud was then returned to the bottle and again rolled overnight at room temperature, and finally mixed another 5 minutes immediately before determining viscosity, gels and water loss by the standard procedure of the American Petroleum Institute.

Fresh water mud test prcedure.T hirty grams of a commercial sodium bentonite rotary drilling clay with a yield value of 92 barrels of 15 centipoise mud per ton of clay were mixed wtih 335 milliliters of distilled water in a Hamilton Beach No. 30 Drinkmaster mixer at 15,000 r.p.m. for 15 minutes and then aged by rolling overnight in pint bottles at room temperature. The thinner additive (each gram added equivalent to 1 pound per barrel) and sodium hydroxide to give the desired pH were then added, the mud mixed 5 minutes, and again rolled overnight at room temperature. A final 5 minute mix was made immediately before measuring viscosity, gels, and water loss by the standard methods of the American Petroleum Institute. The mud may be returned to the bottie and rolled a further 24 hours at 150 F. and then retested to obtain information on the effect of temperature.

Gyp mud test pr0cedure.The gyp (or gypsum base) mud test procedure is the same as the fresh water mud test procedure except that 6 grams (each gram added equivalent to 1 pound per barrel) of plaster of Paris (CaSO /2H O) were added together with the thinner additive, and the mud was subsequently mixed for 20 minutes instead of 5 minutes.

Oil emulsion test pr0cedure.The base mud is prepared as described above and may be any of the types such as lime base, gypsum, fresh water and salt water muds. After adding the thinner additive being tested and making the standard tests for gels, viscosity and water loss, 10 to 20% by weight of diesel oil is mixed into the mud with a high speed mixer at 15,000 r.p.m. and the resulting oil in water emulsion mud tested for gels, viscosity and water loss by the standard API procedures. Note that the term thinner is used in the art in reference to agents or additives for reducing the viscosity of drilling mud.

Example I This example illustrates the improvement in mud thinning properties resulting from heating spent sulfite liquor to a high temperature and simultaneously blowing with air or an inert gas. By way of example and not limitation, the lime mud thinning properties of a sample of fermented spent sulfite liquor heated at 200 C. while blowing with argon were compared with the said properties of the original spent sulfite liquor and those of said liquor heated at the same temperature for the same time without blowing. In addition, the iron salt of the heated and gas blown product was compared with the iron salt of the original spent sulfite liquor as a thinner for gypsum base muds to show that the improvement in thinning properties as a result of the heat treatment is manifest in other types of muds than lime muds. Oxidation of these heat treated samples as described herein above brings about further improvement in the thinning properties.

Concentrated fermented calcium base spent sulfite liquor (218 g.) having 40% by weight of non-volatile solids was neutralized to pH 6.3 with sodium hydroxide and heated to 200 C. in a pressure vessel fitted to permit bubbling gas through the liquor. Sixty-five grams of argon was bubbled through the liquor in 38 minutes, the vessel 28 was cooled and the product liquor dried for testing. The product liquor had a pH of 5.3.

A second sample of the neutralized liquor was heated at 200 C. for 30 minutes in a sealed bomb as a control to determine the effect of heating alone.

Mud tests were made as herein before described using a mud having 45.5 lbs. per barrel of a mixture of clays containing six parts by weight of a commercial drilling clay having a yield value" of 45 barrels of 15 cp. mud per ton and 1 part by weight of a commercial drilling clay having a yield value of barrels of 15 cp. mud per ton of clay.

With reference to Table 1 of Example I heating the liquor at 200 C. for 30 minutes produced a substantial improvement in mud thinning properties and gas blowing brings about a further improvement. This improvement with gas blowing is relatively small and gas blowing is not essential to bringing about the main result of our invention which is the unexpected result of the heat treatment. Furthermore, the effect does not appear to "be due to oxidation, as might be expected with air or oxygen since the improvement over heat treatment is small and the same whether the blowing is done with air, oxygen, nitrogen or other inert gas.

The original spent sulfite liquor and the heated, argon blown samples were also converted to the iron salts by dissolving in water, adding 20% by weight of ferric sulfate (24.5% Fe) as a 25% solution and neutralizing to pH 3.5 with sodium hydroxide. The mixtures were heated to 90 C., centrifuged to remove the precipitates of calcium sulfate and dried at 60 C. These products were tested for thinning of gypsum. base mud. The results in Table 2 of Example I show the improvement gained by the heat treatment. These products may be further improved by oxidation with the agents herein before described in accordance with our invention and discovery.

TABLE 1 OF EXAMPLE I.-EFFECT OF HIGH TEMPERA- TURE HEAT TREATMENT ON LIME MUD THINNING [Tests at 6.0 lbsJbbl. in Limed Mud Rolled 20 Hr. at F.]

TABLE 2 OF EXAMPLE I.EFFECT OF HIGH TEMPE RA- HEAT TREATMENT ON FRESH WATER MUD THIN- [Tests at 4.0 lbsJbbl. in Gyp Mud Rolled 20 Hr. 150 F.]

Sample pH I.G. PV Y 10 G W.L.

Iron Salt of Original Liquor 8. 3 13. 5 5. 5 13. 0 18. 0 16. Iron Salt of Argon Blown 8 Sample 8. 2 1. 5 6. 0 5. 5 12.5 12. 8

By purifying herein is meant partially or completely removing the nonlignosulfonate portions of the spent sulfite liquor as by fermentation, fractionation, lime precipitation in bulk or by small increments, by salting out, or by reaction with organic amines and separation as precipitates or as nonmiscible solutions; in short, by any of the methods known to the art. Particularly, purifying includes the removal of sulfur dioxide, otherwise unnecessary consumption of the oxidizing agent occurs. Such removal may be accomplished by steam stripping and/or air blowing and this particularly at elevated temperatures. Purifying may also include removal of insoluble inorganic precipitates such as calcium sulfite and sulfate. In fractionating we include fractionation with aqueous organic solvents. By separating the spent sulfite liquor solids is meant isolating in whole or in part the said solid components of the spent sulfite liquor by any of the methods herein disclosed. By concentrating the I .29 spent sulfite liquor solids is meant reducing the volatile content of the spent sulfite liquor in part or to the degree that there remain only the solid components of the spent sulfite liquor.

When the phrase, adding to the spent sulfite liquor solid components is used, the solids could be in the original solution or isolated by any of the methods herein mentioned or known to the art. When the statement is herein used treating to form a salt having an element selected from the group consisting of iron, aluminum, chromium, and copper, it is intended, of course, to includecombinations of said elements. Likewise, in the listing of the oxidizing agents, combinations of said agents where chemically feasible are included. When it is directed to add to or treat spent sulfite liquor, it is intended to employ or treat said liquor substantially as received from the digester excepting that the temperature of the spent sulfite liquor may be as it is received from the digester or after the spent sulfite liquor is cooled.

Where; fermented spent sulfite liquor was used, in the examples herein it was prepared from the efiluent from the commercial production of ethyl alcohol by fermentation of spent sulfite liquor with bakers yeast (Saccharomyces ceravisiae. -In the fermentation process the spent sulfite liquor as it is received from the blowpit is stripped (distilled) with steamto remove sulfur dioxide, cooled to.. abou,t,.3 C; and neutralized to about pH 4.5 with lime. Bakers yeast is then added to the neutralized spent sulfite liquor to ferment the hexoes sugars present to alcohol. The fermentation lowers the reducing value of the spent sulfite liquor as measured by Fehlings solution from about 24 percent to about percent expressed as glucose and based onthe spent sulfite liquor solids. Yeast is recovered for reuse by centrifuging and the alcohol is removed from'the fermented liquor by stripping with steam. The resultantliquor is the fermented spent sulfite liquor. This method of fermentation is disclosed more fully iri United States Letters Patent No. 2,430,355, granted to Joseph L. McCarthy on November 4, 1947. Any method of fermentation which primarily utilizes the carbohydrates may be used. The fermentation may be either anaerobic or aerobic by any of a number of microorganisms including bacteria and yeast of the Torula genus.

In using a gypsum base mud, the calcium sulfate may be added to the mud from the strata being drilled.

Where examples of substances are given it is to be understood the same is done by way of illustration and not limitation.

We claim:

1. A drilling fluid composition comprising a suspension of a clayey material in an aqueous medium containing an effective dispersing amount of a soluble oxidized salt of a sulfonated lignin-containing material which has been heat treated at a temperature between about 170 C. and 210 C. and higher temperatures, said salt having a cation selected from the group consisting of iron, aluminum, chromium, copper and mixtures thereof.

2. The composition of claim 1 wherein said sulfonated lignin-containing material is obtained from spent sulfite liquor and wherein said oxidizing agent is selected from the group consisting of hydrogen peroxide, ozone, lead dioxide, chromic acid, chlorine, alkali metal and alkaline earth metal hypochlorites, alkali metal chromate, alkali metal permanganate, alkali metal persulfate, alkali metal perborate, electrolytic oxidation and combinations thereof.

3. The composition of claim 2 wherein said cation is iron and said oxidizing agent is an alkali metal chromate.

4. A drilling fluid composition comprising a suspension of a clayey material in an aqueous medium containing an effective dispersing amount of a soluble salt of a sulfonated lignin-containin'g material which has been heat treated at a temperature between about 170 C. and 210 C. and higher temperatures, said soluble salt having 30 a cation selected from the group consisting of iron, aluminum, chromium, copper and mixtures thereof.

5. The composition of claim 4 wherein said sulfonated lignin-containing material is obtained from spent sulfite liquor.

6. The composition of claim 5 wherein said cation is iron.

7. A drilling fluid composition comprising a suspension of a clayey material in an aqueous medium containing an effective dispersing amount of a soluble oxidized sulfonated lignin-containing material which has been treated at a temperature between about C. and 210 C. and higher temperatures, said sulfonated lignin-containing material being oxidized with an oxidizing agent having an oxidizing power stronger than an oxidation potential of about l.3.

8. The composition of claim 7 wherein said sulfonated lignin-containing material is obtained from spent sulfite liquor and wherein said oxidizing agent is selected from the group consisting of hydrogen peroxide, ozone, lead dioxide, chromic acid, chlorine, alkali metal and alkaline earth metal hypochlorites, alkali metal chromate, alkali metal permanganate, alkali metal persulfate, alkali metal perborate, electrolytic oxidation and combinations thereof.

9. A drilling fluid composition resistant to the effects of temperature, contamination and heaving shale, said composition comprising a suspension of a clayey material in an aqueous medium, an excess of calcium sulfate over its solubility in the aqueous medium and l20 pounds per barrel of said drilling fluid of'a soluble oxidized salt of a sulfonated lignin-containing material which has been heat treated in solution at a temperature between about 170 C. and 210 C., said salt having a cation selected from the group consisting of iron, aluminum, chromium, copper and mixtures thereof, and said material having been oxidized with an oxidizing agent selected from the group consisting of hydrogen peroxide, ozone, lead dioxide, chromic acid, chlorine, alkali metal and alkaline earth metal hypochlorites, alkali metal chromate, alkali metal permanganate, alkali metal persulfate, alkali metal perborate, electrolytic oxidation and combinations thereof.

10. A drilling fluid composition comprising a suspension of a clayey material in an aqueous medium, containing an effective dispersing amount of an additive prepared by heat treating a sulfonated lignin-containing material at a temperature between about 170 C. and 210 C., and interacting said sulfonated lignin-containing material with a soluble metal ion selected from the group consisting of iron, aluminum, chromium, copper and mixtures thereof, said metal ion being present in an amount chemically equivalent to 1-50% of the sulfate salt thereof, based on the weight of the sulfonated lignin-solids.

11. A drilling fluid composition comprising a suspension of a clayey material in an aqueous medium containing an effective dispersing amount of an additive comprising a sulfonated lignin-containing material which has been complexed with a metal selected from the group consisting of iron, aluminum, chromium, copper and mixtures thereof, said material having been heat treated at a temperature between about 170 C. and 210 C., to produce a soluble product, said metal being present in an amount chemically equivalent to 1-50% of the sulfate salt thereof, based on the weight of the sulfonated lignin in said material.

12. The composition of claim 11 wherein said material has been oxidized with an oxidizing agent selected from the group consisting of hydrogen peroxide, ozone, lead dioxide, chromic acid, chlorine, alkali metal and alkaline earth metal hypochlorites, alkali metal chromate, alkali metal permanganate, alkali metal persulfate, alkali metal peroorate, electrolytic oxidation and combinations thereof.

13. A drilling fluid composition comprising a suspension of a clayey material in an aqueous medium containing an effective dispersing amount of an additive comprising a sulfonated lignin-containing material in combination with a metal in soluble form selected from the group consisting of iron, aluminum, copper, chromium and mixtures thereof, said metal being present in an amount chemically equivalent to 1-50% of the sulfate salt thereof, based on the weight of the sulfonated lignin in the material, said material having been heat treated at a temperature between about 170 C. and 210 C. to produce a soluble product.

14. A drilling fluid composition comprising a suspension of a clayey material in an aqueous medium containing an effective dispersing amount of an additive comprising a soluble sulfonated lignin-containing material which has been heat treated at a temperature between about 170 C. and 210 C. to produce a soluble product, and a soluble metal ion selected from the group consisting of iron, aluminum, copper, chromium and mixtures thereof, said metal ion being present in an amount chemically equivalent to 1-50% of the sulfate salt thereof, based on the weight of the sulfonated lignin in the material, and said sulfonated lignin-containing material and said metal ion being present in said suspension in an amount sufficient to improve at least one of the gel strength, viscosity and water loss properties of said suspension.

15. A method of drilling a well comprising circulating in the well a well drilling fluid comprising the composition of claim 1.

16. A method of drilling a well comprising circulating in the well a well drilling fluid comprising the composition of claim 2.

17. A method of drilling a well comprising circulating in the well a well drilling fluid comprising the composition of claim 3.

18. A method of drilling a Well comprising circulating in the well a well drilling fluid comprising the composition of claim 4.

19. A method of drilling a well comprising circulating in the Well a well drilling fluid comprising the composi tion of claim 5.

20. A method of drilling a well comprising circulating in the well a well drilling fluid com-prising the composition of claim 6.

21. A method of drilling a well comprising circulating in the well a well drilling fluid comprising the composition of claim 7.

22. A method of drilling a well comprising circulating in the well a well drilling fluid comprising the composition of claim 8.

23. A method of drilling a well comprising circulating in the well a well drilling fluid comprising the composition of claim 9.

24. A method of drilling a well comprising circulating in the well a well drilling fluid comprising the composition of claim 10.

25. A method of drilling a well comprising circulating in the well a well drilling fluid comprising the composition of claim 11.

26. A method of drilling a well comprising circulating in the well a well drilling fluid comprising the composition of claim 12.

27. A method of drilling a well comprising circulating in the well a well drilling fluid comprising the composition of claim 13.

28. A method of drilling a well comprising circulating in the well a Well drilling fluid comprising the composition of claim 14.

References Cited by the Examiner UNITED STATES PATENTS 2,858,271 10/1958 Byrd 2528.5 2,935,473 5/1960 King et al. 2528.5 3,025,235 3/1962 Smith et al. 2528.5 3,087,923 4/1963 King et al. 2528.5

JULIUS GREENWALD, Primary Examiner. 

1. A DRILLING FLUID COMPOSITION COMPRISING A SUSPENSION OF A CLAYEY MATERIAL IN AN AQUEOUS MEDIUM CONTAINING AN EFFECTIVE DISPERSING AMOUNT OF A SOLUBLE OXIDIZED SALT OF A SULFONATED LIGNIN-CONTAINING MATERIAL WHICH HAS BEEN HEAT TREATED AT A TEMPERATURE BETWEE ABOUT 170*C. AND 210*C. AND HIGHER TEMPERATURES, SAID SALT HAVING A CATION SELECTED FROM THE GROUP CONSISTING OF IRON, ALUMINUM, CHROMIUM, COPPER AND MIXTURES THEREOF.
 4. A DRILLING FLUID COMPOSITION A SUSPENSION OF A CLAYEY MATERIAL IN AN AQUEOUS MEDIUM CONTAINING AN EFFECTIVE DISPERSING AMOUNT OF A SOLUBLE SALT OF A SULFONATED LIGNIN-CONTAINING MATERIAL WHICH HAS BEEN HEAT TREATED AT A TEMPERATURE BETWEEN ABOUT 170*C. AND 210*C. AND HIGHER TEMPERATURES, SAID SOLUBLE SALT HAVING A CATION SELECTED FROM THE GROUP CONSISTING OF IRON, ALUMINUM, CHROMIUM, COPPER AND MIXTURES THEREOF.
 7. A DRILLING FLUID COMPOSITION COMPRISING A SUSPENSION OF A CLAYEY MATERIAL IN AN AQUEOUS MEDIUM CONTAINING AN EFFECTIVE DISPERSING AMOUNT OF A SOLUBLE OXIDIZED SULFONATED LIGNIN-CONTAINING MATERIAL WHICH HAS BEEN TREATED AT A TEMPERATURE BETWEEN ABOUT 170*C. AND 210* C. AND HIGHER TEMPERATURES, SAID SULFONATED LIGNIN-CONTAINING MATERIAL BEING OXIDIZED WITH AN OXIDIZING AGENT HAVING AN OXIDIZING POWER STRONGER THAN AN OXIDATION POTENTIAL OF ABOUT -1.3. 